The present invention relates to a degradable foam and the method for its production, more specifically, the present invention relates to a lignocellulose solution, with lignocellulose and/or its derivatives dissolved in aliphatic polyester polyol of low molecular weight, and the method for production of this solution; to a foam of excellent biodegradability obtained by foaming and hardening (cross-linking) said lignocellulose solution by an ordinary foaming agent and a hardening agent, and the method for production of this foam; to a foam of excellent photodegradability as well as biodegradability obtained by the same method after adding a photodegradation promoters to said solution and the method for production of this foam.
And the present invention also relates to a lignocellulose solution, with a lignocellulose and/or its derivatives dissolved in bio-/photo-degradable aliphatic polyester polyol of low molecular weight, and the method for production of this solution; and to a foam of excellent photodegradability as well as biodegradability obtained by foaming and hardening said lignocellulose solution with ordinary foaming and hardening agents.
These days waste plastic is regarded as one of the main reasons of environmental pollution, and so how to dispose of this waste plastic has been a serious problem in many countries, especially in the industrially advanced nations. Formerly waste plastic was disposed by burying, incineration, or recycling, but burying is confronting a capacity limit, while incineration is causing not merely unnecessary waste of energy, influencing unfavorable rise of the global temperatures due to generation of carbon dioxide, but also a problem in economic aspects due to damages of incinerators. Meanwhile recycling is looked upon as an ideal means and a great deal of research on it is being made, but it is still faced with much difficulty for want of cost-efficient ways of collection, quality control, standards, etc.
Especially, the polystyrene foam widely used as a disposable filler for packing is apt to be bulky and thus aggravates the shortage of burial land and incineration and recycling also have problems as has been remarked above, causing the environmental pollution. Many a country is in a hurry meeting such problems by many kinds of countermeasures, for example, application of restraints by law.
Now, therefore, brisk efforts have been made to solve the problem of the foam used as filler by making it automatically recycle to nature by means of conferring upon it a bio-/photo-degradability so that it can be degraded by the sun light or microorganisms in a certain period of time after disposal. For example, a biodegradable foam (sold under the name of NOVON), made of starch and water-soluble polymer, has been developed by a U.S. maker, NOVON PRODUCT CO. However, this product contains much starch, and so its hygroscopicity is too high, its physical properties like impact resistance are somewhat poor, and, moreover, it is not affordable for popular use. Japan's Showa High Polymer, Co., Ltd. has also succeeded in production of a synthetic biodegradable aliphatic polyester foam (sold under the name of BIONOLLE) and is in an immediate plan for its mass production, but this also is anticipated to face difficulty in a commercial aspect.
In the meantime, lignocellulose means a material including cellulose, hemicellulose, lignin etc., such as wooden powder, rice bran, straw, etc. Although these have properties of easy degradation by microorganisms in the nature and at the same time a crystalline structure contributory to desirable physical properties, they have many other problems including lack of thermoplasticity, and for these reasons they are simply discarded. Still, there is an urgant need to develop the proper ways for highly productive use of tremendous amount of these waste materials.